The perfect model
According to this tweet, there is not a better mirror for you than your identical twin. What makes it so much more effective than a regular mirror is you are getting not a 2-dimensional version, but a 3-dimensional one! Just imagine it. You can go into any clothing store you want. You try on that cute outfit that you really like, and you check yourself out in the mirror where you have to strain your neck as you turn around to see the sides and the back. Now imagine having your identical twin model it for you from any angle you like!